1. Field of the Invention
The present invention relates to a lithium rechargeable battery, and more particularly, to a lithium rechargeable battery having outer covers, each having ribs formed on an inner surface of the outer covers, coupled to both sides of a core pack, which makes it possible to prevent resin from flowing into the outer covers when resin molding parting is performed on an upper part of the core pack and thus reduces defects occurring in the outer covers due to the flow of resin.
2. Description of the Related Art
In general, as the light-weightness and high-functionality of portable radio apparatuses, such as video cameras, mobile phones, and portable computers, have continued to progress, numerous researches for rechargeable batteries used as power sources have been made. Such rechargeable batteries include, for example, a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-zinc battery, and a lithium rechargeable battery. Among them, the lithium rechargeable battery that can be made in a small size with a high capacity has come into widespread use in the field of high-tech electronic apparatuses due to its advantages such as a high operation voltage and a high energy density per unit weight.
A lithium rechargeable battery pack is formed in such a manner that, after safety devices, such as a PTC (positive temperature coefficient) element, a thermal fuse, and a protective circuit module (hereinafter, referred to as a PCM), are mounted to a bare cell which has an electrode assembly having a positive electrode plate, a negative electrode plate, and a separator, a can for housing the electrode assembly and an electrolyte, and a cap assembly sealing up a top side opening of the can, the bare cell having the safety devices mounted thereto is put into a separate case, or gaps in the bare cell are filled up with a hot-melt resin and a tubing process using a thin wrapping material and a labeling process are sequentially performed on the bare cell.
The safety device is connected to a positive electrode terminal and a negative electrode terminal of the bare cell through lead plates, said lead plates are conductive members, to break an electric current when an internal temperature of the battery increases or a voltage rises due to the overcharge of the battery, thereby preventing the combustion and/or explosion of the battery.
A battery pack according to the related art includes: a core pack that includes a bare cell capable of performing discharge and charge and having an electrode terminal protruding from one short lateral side thereof and a protective circuit module connected to the top side of the bare cell; a resin molding part that is formed by a hot-melt method using a hot-melt resin at an upper part of the core pack having the protective circuit module, to be mounted on an external set and to prevent the protective circuit module separating from the bare cell; and outer covers that cover both sides of the core pack to form a portion of the appearance of the battery pack.
In such a battery pack, an electrode terminal protruding from one short lateral side of the bare cell and other short lateral side of the bare cell having a polarity opposite to that of the electrode terminal are electrically connected to electrical connection terminals formed on the protective circuit module that is provided on the top side of the bare cell through lead plates each bent in a substantially “L” shape, respectively. That is, respectively, one end of each lead plate is electrically connected to the electrode terminal protruding from one short lateral side and the other short lateral side of the bare cell, and the other end of each lead plate is electrically connected to the electrical connection terminals of the protective circuit module arranged on the top side of the bare cell. Herein, the one short lateral side and the other short lateral side of the bare cell mean sides having a small width among the sides of the bare cell except for the top side of the bare cell on which the protective circuit module is arranged and the bottom side opposite to the top side.
In this way, since the ends of each lead plate are respectively connected to the electrode terminal protruding from one short lateral side and the other short lateral side of the bare cell, the lead plates are exposed from one short lateral side and the other short lateral side of the bare cell, respectively. Therefore, in order to cover one short lateral side and the other short lateral side of the bare cell, outer covers are coupled to one short lateral side and the other short lateral side of the bare cell. In this case, a gap is formed between the one short lateral side of the bare cell and the outer cover due to the lead plate connected to one short lateral side of the bare cell. In addition, a gap is formed between the other short lateral side of the bare cell and the outer cover due to the lead plate connected to the other short lateral side of the bare cell.
Therefore, when the outer covers are coupled to one short lateral side and the other short lateral side of the bare cell and then a hot-melt resin is filled into a gap between the protective circuit module and the bare cell so as to form a resin molding part, a fluid hot-melt resin flows in the downward direction of the outer covers through the gaps between the outer covers and one short lateral side and the other short lateral side of the bare cell.
However, when the hot-melt resin continuously flows into the gaps in the downward direction of the outer covers due to high pressure even after the gaps are filled up with the hot-melt resin, the hot-melt resin leaks from the outer covers to the outside due to high pressure. As a result, defects occurring in the appearance of the battery pack results in an increase of the defect rate of a battery pack.